1. Field of the Invention
This invention relates to a tool for expanding tubular members and particularly to a tool for expanding selected portions of tubes by hydraulic means. More specifically, the present invention is directed to a technique for the repair of steam generator tubes and especially to a method for securing repair sleeves within such tubes. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
2. Description of the Prior Art
A recurring problem in the power generation industry is the deterioration of steam generator tubes. Steam generator tube deterioration leads to the development of cracks and ultimately to leakage through the tube walls. The repair of deteriorated steam generator tubes conventionally involves installing a metal sleeve inside the deteriorated tube, the sleeve extending upstream and downstream at the leakage site. The tube/sleeve assembly is then radially expanded so that intimate surface-to-surface contact is established between the repair sleeve and the deteriorated tube. Various welding techniques may then be employed to bond the deteriorated tube to the repair sleeve to enhance the tight fluid seal between the sleeve and the generator tube.
The expansion process conventionally involves the use of a hydraulic operating fluid, i.e., the interior of the sleeve is pressurized with the operating fluid to cause radial expansion thereof. A residue of the hydraulic fluid which contacts the sleeve may remain on the interior surface thereof after the expansion process is completed. This residual fluid may adversely affect the integrity of the welding which is subsequently undertaken to complete the tube/sleeve bonding process. The present invention is directed to a new and improved tube expansion method and tool which employs a hydraulic operating fluid and wherein fluid contact with the tube/sleeve assembly is avoided.